This invention relates to an optical head for reading/writing digital data on a recording medium and more particularly to an optical head having a photo detector mounted on a tab extending from the head gimbal assembly.
U.S. Pat. No. 4,860,276, Ukita et al. and U.S. Pat. No. 5,625,617, Hopkins et al. disclose optical heads for optical data recording systems. In the optical heads depicted in these patents the detector is either part of the laser structure, is attached to the slider, or light is piped to the detector via an optical fiber, or mirror and lens optical path.
U.S. Pat. No. 4,167,765, Watrous discloses a head gimbal assembly for heads of a type which is commonly referred to as Winchester. These are commonly used for magnetic recording on hard disk drives. The present invention relates to an optical head in which the laser is mounted on a head gimbal assembly of this type.
In accordance with the present invention the head gimbal assembly of an optical head has a tab extending therefrom. A photo detector is mounted on the tab of the head gimbal assembly. In one embodiment the photo detector is mounted on the load beam of the head gimbal assembly and in another embodiment the photo detector is mounted on the flexure of the head gimbal assembly.
In accordance with the present invention a separate detector is mounted in the optical path of the laser in close proximity and with or without an angular offset. The tab is bendable so that it can be deformed so that minimal or reduced optical feedback from the source laser is provided. The tab can be bent to an off optical axis angle thereby preventing a path for reflection to return into the laser diode.
The separate detector can be independently tested prior to the more costly attachment of the laser/slider assembly thereby saving the cost of the more costly components in the event of a photo-detector failure during the manufacturing process.
In accordance with the invention the mounting tab has preformed locator features for positioning the photo detector optimally. These preformed features may be used for easy application of the bonding adhesive, flex circuit or solders.
Further in accordance with the invention a flex circuit is mounted through the load beam or flexured tab to provide electrical connection and structural support to the photo detector and electrical connection to the laser diode. By mounting the detector onto the load beam of the head gimbal assembly, the effects of the detector""s electrical connections will not be imparted onto the moving/gimballing components of the head gimbal assembly.
By using a position type of detector and the active feedback of this detector while the laser is active the positioning of the slider relative to the dimple of the suspension can be detected and adjusted prior to attachment of the head to the gimbal. This requires proper sizing and positioning of the detector onto the suspension and specially designed tooling.